Measuring a viscosity of a material is an indispensable technique for quality control, performance evaluation, material control, and research and development in manufacturing process of medicines, foods, coatings, inks, cosmetics, chemicals, papers, adhesives, fiber, plastics, beer, detergents, concrete admixture, and silicon or the like.
The methods of measuring viscosity are a method using a capillary tube, a method by contacting an oscillator with a sample, a method using a rotator, and so on.
The method using a rotator, one of the above-mentioned methods, is disclosed in International Publication No. WO 2009/131185 (International Patent Application No. PCT/JP2009/058089).
Specifically, it is configured so as to sink a conductive rotator (sphere) into a container containing a sample liquid, and apply a rotating magnetic field to the rotator from an outside of the container.
Under such configuration, when the rotating magnetic field is applied to the rotator, Lorentz force works between the electric current generated on the rotator and the rotating magnetic field, and the rotator rotates along with the rotating magnetic field. At this time, since the rotating velocity of the rotator delays depending on the viscosity of the sample from the rotating velocity of the rotating magnetic field, the viscosity can be calculated based on this relationship.
The difference between the rotating velocity of the rotator and the rotating velocity of the rotating magnetic field can be expressed by a linear equation having a specific slope. The slope of the linear equation becomes the viscosity.